1. Field of the Invention
This invention relates to the lamination of assemblies comprising glass and flexible plastic sheets. Laminated glass assemblies have been developed for various uses. Large glazing closures have been used in buildings. Smaller glazing closures have been used in automobiles, aircraft, other vehicles and instrument panels.
According to a typical prior art laminating technique, an assembly is formed by building up alternate sheets of glass and flexible interlayer material until the requisite number of sheets are assembled. The assembly is enclosed within an endless deairing ring comprising one or more channel-shaped members of a fluid-impervious material. The deairing ring engages the outer surfaces of a marginal portion only of the assembly and has a base portion spaced from the periphery of the assembly to provide a conduit around the margin of the assembly. The conduit is connected to a source of vacuum, and the air and other fluid that may be entrapped between the sheets of the assembly is removed by evacuation through the deairing ring.
When the fluid is removed from the interfacial surfaces of the assembly, the major surfaces of the assembly are subjected to approximately atmospheric pressure. After the evacuation proceeds for awhile, the assembly is heated to an elevated temperature sufficient to bond the glas sheets to the interlayer sheet or sheets, depending upon the number of sheets to be laminated.
A discussion of patents of interest which follows will indicate some of the problems involved in the method of laminating glass sheets using the deairing rings of the prior art.
2. Description of Patents of Interest
U.S. Pat. No. 1,870,284 to Drake discloses the use of rigid peripheral evacuation chambers to apply suction to two adjacent sides of an assembly of glass and interlayer sheets to evacuate air from the interfaces between the sheets during the lamination of the assembly. These evacuation chambers had to be aligned exactly with the thickness of the assembly undergoing evacuation because of a lack of flexible lips that engage the outside major surfaces of the assembly.
U.S. Pat. No. 2,948,645 to Keim discloses using a deairing ring comprising an endless, flexible, air-impervious channel-shaped member having flexible lips that fit over the outer edge portions of an assembly of curved glass sheets and a flexible interlayer sheet to be laminated. The channel member has a base spaced from the edge of the assembly to define a peripheral evacuation chamber around the assembly. A vacuum pipe connects to the chamber to suck fluid via the evacuation chamber from the interfaces between the elements of the assembly. A porous tape that extends completely around the assembly may be disposed within the channel-shaped member. The gist of this patent requires that the evacuation channel extend around the complete periphery of the assembly. Thus, each different outline shape of an assembly to be laminated requires a different shape for the channel-shaped member that defines the evacuation chamber. Other patents that enclose the peripheral edge of an assembly to be laminated within the lips of a deairing ring comprising a flexible channel member includes U.S. Pat. No. 2,992,953 to Talburtt, U.S. Pat. Nos. 3,074,466 and 3,074,838 to Little, U.S. Pat. No. 3,100,173 to Boicey et al., U.S. Pat. No. 3,234,062 to Morris, U.S. Pat. No. 3,249,479 to Boicey, U.S. Pat. No. 3,281,296 to Jameson and U.S. Pat. No. 3,852,136 to Plumat et al.
In all of these latter patents except for the Talburtt patent, the flexible channel members extend continuously around the periphery of the assembly to be laminated. Therefore, it is necessary to maintain an inventory of flexible channel members for each production pattern. The storage and inventory problem is tremendous. Also, the fabrication of such channel members is expensive, as it requires a separate mold for each pattern if the channel member is made in one piece, or several molds followed by a vulcanizing step if the channel member is made in sections.
U.S. Pat. No. 2,992,953 to Talburtt discloses a deairing ring formed from a grooved supporting strip and a cooperating length of flexible channel tubing that is adapted to be wrapped about the periphery of the assembly and anchored to the grooved supporting strip. The invention covered by this patent represents an improvement over the endless rings of the other patents in that the Talburtt deairing ring is not limited to specific size and is not as difficult to apply and allegedly does not require as much time to apply as the endless rings of the other patents. Instead, the Talburtt deairing ring is applied by mounting a bottom edge of the assembly into the grooved supporting strip, applying the flexible channel tubing about the remainder of the periphery of the assembly and clamping appropriate portions of the flexible channel tubing to the ends of the grooved supporting strip, leaving a length of the flexible channel tubing beyond each clamped portion. Different lengths of flexible channel tubing remain for different patterns depending on the length of the perimeter of the assembly to be laminated.
The Talburtt invention is limited in its application to automobile windshields that have an edge straight enough to be received within the grooved supporting strip and corners of sufficiently rounded configuration to enable the application of the flexible channel tubing to the periphery of the assembly without having the tubing buckle in the vicinity of any sharp corners. The Talburtt deairing rings would not be suitable for use in laminating large windows of rectangular configuration or of any polygonal configuration that incorporates sharp corners, such as are used in buildings. Furthermore, the Talburtt deairing ring is provided in its flexible channel tubing with a single tube-like connection to a vacuum line. This single vacuum connection limits the maximum size of assembly that can be evacuated in a practical manner to a size comparable to that of an automobile windshield, which is much smaller in area than laminated windows used in architectural glazing. Large size windows are more difficult to laminate using peripheral suction than smaller size windows. Furthermore, some laminated architectural glazing comprises a sheet of glass that is coated on the surface to be laminated to the interlayer. Such a coated surface is usually more difficult to adhere to an interlayer than uncoated glass.
It will be understood that the art of laminating glass sheets using deairing rings required further improvements, particularly in the lamination of extremely large laminated windows to be used for architectural purposes, and particularly windows having sharp corners. It is understood, however, that the principles incorporated in the present invention may also be used in the fabrication of smaller windows such as those found in vehicles and in certain instrument windows.